Vibration help

reborn55 · December 05, 2009, 07:59:39 PM

Got the big brake setup installed on ragtop today--took for a ride and all braking is well--still pulls left once in awhile. Problem is I still have a front end vibration/shimmy in the steering wheel. Was hoping rotors and brackets would cure it. Still wanted the big brakes anyway. The front end is new--every single part has been replaced. Was fine for awhile and then the steering wheels started to shimmy. Different wheels and tires change but do not get rid of it. Took the wheels and tires off and put them on wifes coupe and smooth as glass on her car. I am running out of patience and money trying to cure this pain the a_ _ problem. Any suggestions.
Thanks

UGLY OLDS · December 05, 2009, 08:17:55 PM

Alignment

How much positive caster

?

How much wheel offset?

Bob.......

wayne petty · December 05, 2009, 08:21:44 PM

is it possible to put in more positive caster?

does it still have the same rack and pinion?

?

does anybody know... on a tbird M2 rack... is there a tension spring under a cap to keeps the rack tight against the pinion..

? is there an adjustment in there some how???

is there any play in the steering shaft between the rack and the wheel?

have you tried it with the power steering belt disconnected??? perhaps its in the rack itself???

just a thought...

reborn55 · December 05, 2009, 08:32:18 PM

Was perfect until on a trip to Louisville the vibration came beck--had had it when I first bought the car and it was the caliper mounting brackets that were loose. tighten them up and all was well. about a year later going to Louisville the vibration came back, been fighting it ever since. Not at all speeds--upwards of 65 seems better. Thanks

river1 · December 05, 2009, 08:38:27 PM

thinking out loud here

bent spindle?
cracked spindle?

later jim

enjenjo · December 05, 2009, 08:42:44 PM

See if you have a loose inner tie rod end.

wayne petty · December 05, 2009, 09:16:14 PM

at speeds upwards of 65?

?/

who has been balancing your tires?

? same shop.. same machine...

might be too old a machine to hold a good calibration...

a lot of older machines were only set to get close enough for 55 mph...

we had an FMC in the shop back in the early 90's... brand new... it could not balance a tire to go 80... it would come back with a complaint of tire shake at speed...

have you gotten somebody to drive next to you to see which way the tire is shaking??? back and forth... or up and down?

do you have the ability to set up a rig to let the mounted tire... sit centered on a horizontal shaft that is supported on shielded bearings.. no drag... see if the tire rotates on its own... set it at quarter turns.. see if it moves.. .,...

is there any run out in your wheels or tires when they are mounted on the rotors

??

you say the alignment is good.. but what are your settings?

? something is wrong.. or you would not have a wobble... or a shake...

make my shake strawberry.... with whipped topping...

wayne out... i think i took this train before...

reborn55 · December 05, 2009, 09:17:40 PM

Didn't see any problems with the spindles. Inner tie rods are good I think--rack has been replaced.. I will double check that romorrow. As far as I can tell all is tight and alignment is good.

reborn55 · December 05, 2009, 09:25:16 PM

Does not matter what wheels and tires I use. Can take the front wheels and tires off on put on wife's 48 Chevy coupe and it is smooth as glass.

Had the front wheels and tires road force balanced

wayne petty · December 05, 2009, 09:34:21 PM

get someone along side of you out on the highway... have them look at your tires... its better if the person is a professional wheel alignment tech... they deal with this stuff every day..

enjenjo · December 05, 2009, 09:48:17 PM

Quote from: "reborn55"Didn't see any problems with the spindles. Inner tie rods are good I think--rack has been replaced.. I will double check that romorrow. As far as I can tell all is tight and alignment is good.

I have bought rebuilt racks with loose inner tie rod ends. Some rebuilders don't even check them.

reborn55 · December 05, 2009, 10:12:26 PM

Looking at the time frame when I put the rack in was before I found the caliper brackets loose. Had some vibration before and after the rack was installed. Will look at it tomorrow. thanks

40cpe · December 12, 2009, 02:22:15 PM

I posted here back in the early summer because my car with a MII front end was shaking at higher speeds. It had new tires, alignment, all tight front parts, etc. One of the suggestions was to make sure the rack was centered. It wasn't far off, about 1/8 turn of the steering wheel, but in the process of adjusting that I changed my toe in from about 1/8" to less than 1/16th. I decided to see if that made a difference. I played with tire pressure a little, but ended up at about 28 psi. I took a 1200 mile weekend trip in October and didn't have any shaking. I'm thinking the toe in was the culprit. As mentioned in the discussion, frame modifications sometime set up weird characteristics and just a little change in some settings can make a difference.

Leon · December 12, 2009, 04:01:03 PM

I had a shake once and found it was toe. One tire would fight the other, when I got the toe-in right it went away.

reborn55 · December 12, 2009, 04:39:40 PM

Really appreciate all the input. What I don't understand is why it can be absolutely beautiful for about 1200 miles and then go wacko. I know things wear out, but I haven't owned the car long enough for the all the new parts to wear out that I have put on. Went out and put extra washers on strut rod bushing thinking they might not be seated all the way. Was going to drive it and then move wife's coupe over so I get work on it. Thanks.